// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package com.google.protobuf;

import java.lang.reflect.Field;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.security.AccessController;
import java.security.PrivilegedExceptionAction;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Utility class for working with unsafe operations.
 */
final class UnsafeUtil {
    private static final sun.misc.Unsafe UNSAFE = getUnsafe();
    private static final Class<?> MEMORY_CLASS = Android.getMemoryClass();
    private static final boolean IS_ANDROID_64 = determineAndroidSupportByAddressSize(long.class);
    private static final boolean IS_ANDROID_32 = determineAndroidSupportByAddressSize(int.class);
    private static final MemoryAccessor MEMORY_ACCESSOR = getMemoryAccessor();
    private static final boolean HAS_UNSAFE_BYTEBUFFER_OPERATIONS =
            supportsUnsafeByteBufferOperations();
    private static final boolean HAS_UNSAFE_ARRAY_OPERATIONS = supportsUnsafeArrayOperations();

    static final long BYTE_ARRAY_BASE_OFFSET = arrayBaseOffset(byte[].class);
    // Micro-optimization: we can assume a scale of 1 and skip the multiply
    // private static final long BYTE_ARRAY_INDEX_SCALE = 1;

    private static final long BOOLEAN_ARRAY_BASE_OFFSET = arrayBaseOffset(boolean[].class);
    private static final long BOOLEAN_ARRAY_INDEX_SCALE = arrayIndexScale(boolean[].class);

    private static final long INT_ARRAY_BASE_OFFSET = arrayBaseOffset(int[].class);
    private static final long INT_ARRAY_INDEX_SCALE = arrayIndexScale(int[].class);

    private static final long LONG_ARRAY_BASE_OFFSET = arrayBaseOffset(long[].class);
    private static final long LONG_ARRAY_INDEX_SCALE = arrayIndexScale(long[].class);

    private static final long FLOAT_ARRAY_BASE_OFFSET = arrayBaseOffset(float[].class);
    private static final long FLOAT_ARRAY_INDEX_SCALE = arrayIndexScale(float[].class);

    private static final long DOUBLE_ARRAY_BASE_OFFSET = arrayBaseOffset(double[].class);
    private static final long DOUBLE_ARRAY_INDEX_SCALE = arrayIndexScale(double[].class);

    private static final long OBJECT_ARRAY_BASE_OFFSET = arrayBaseOffset(Object[].class);
    private static final long OBJECT_ARRAY_INDEX_SCALE = arrayIndexScale(Object[].class);

    private static final long BUFFER_ADDRESS_OFFSET = fieldOffset(bufferAddressField());

    private static final int STRIDE = 8;
    private static final int STRIDE_ALIGNMENT_MASK = STRIDE - 1;
    private static final int BYTE_ARRAY_ALIGNMENT =
            (int) (BYTE_ARRAY_BASE_OFFSET & STRIDE_ALIGNMENT_MASK);

    static final boolean IS_BIG_ENDIAN = ByteOrder.nativeOrder() == ByteOrder.BIG_ENDIAN;

    private UnsafeUtil() {
    }

    static boolean hasUnsafeArrayOperations() {
        return HAS_UNSAFE_ARRAY_OPERATIONS;
    }

    static boolean hasUnsafeByteBufferOperations() {
        return HAS_UNSAFE_BYTEBUFFER_OPERATIONS;
    }

    static boolean isAndroid64() {
        return IS_ANDROID_64;
    }

    @SuppressWarnings("unchecked") // safe by method contract
    static <T> T allocateInstance(Class<T> clazz) {
        try {
            return (T) UNSAFE.allocateInstance(clazz);
        } catch (InstantiationException e) {
            throw new IllegalStateException(e);
        }
    }

    static long objectFieldOffset(Field field) {
        return MEMORY_ACCESSOR.objectFieldOffset(field);
    }

    private static int arrayBaseOffset(Class<?> clazz) {
        return HAS_UNSAFE_ARRAY_OPERATIONS ? MEMORY_ACCESSOR.arrayBaseOffset(clazz) : -1;
    }

    private static int arrayIndexScale(Class<?> clazz) {
        return HAS_UNSAFE_ARRAY_OPERATIONS ? MEMORY_ACCESSOR.arrayIndexScale(clazz) : -1;
    }

    static byte getByte(Object target, long offset) {
        return MEMORY_ACCESSOR.getByte(target, offset);
    }

    static void putByte(Object target, long offset, byte value) {
        MEMORY_ACCESSOR.putByte(target, offset, value);
    }

    static int getInt(Object target, long offset) {
        return MEMORY_ACCESSOR.getInt(target, offset);
    }

    static void putInt(Object target, long offset, int value) {
        MEMORY_ACCESSOR.putInt(target, offset, value);
    }

    static long getLong(Object target, long offset) {
        return MEMORY_ACCESSOR.getLong(target, offset);
    }

    static void putLong(Object target, long offset, long value) {
        MEMORY_ACCESSOR.putLong(target, offset, value);
    }

    static boolean getBoolean(Object target, long offset) {
        return MEMORY_ACCESSOR.getBoolean(target, offset);
    }

    static void putBoolean(Object target, long offset, boolean value) {
        MEMORY_ACCESSOR.putBoolean(target, offset, value);
    }

    static float getFloat(Object target, long offset) {
        return MEMORY_ACCESSOR.getFloat(target, offset);
    }

    static void putFloat(Object target, long offset, float value) {
        MEMORY_ACCESSOR.putFloat(target, offset, value);
    }

    static double getDouble(Object target, long offset) {
        return MEMORY_ACCESSOR.getDouble(target, offset);
    }

    static void putDouble(Object target, long offset, double value) {
        MEMORY_ACCESSOR.putDouble(target, offset, value);
    }

    static Object getObject(Object target, long offset) {
        return MEMORY_ACCESSOR.getObject(target, offset);
    }

    static void putObject(Object target, long offset, Object value) {
        MEMORY_ACCESSOR.putObject(target, offset, value);
    }

    static byte getByte(byte[] target, long index) {
        return MEMORY_ACCESSOR.getByte(target, BYTE_ARRAY_BASE_OFFSET + index);
    }

    static void putByte(byte[] target, long index, byte value) {
        MEMORY_ACCESSOR.putByte(target, BYTE_ARRAY_BASE_OFFSET + index, value);
    }

    static int getInt(int[] target, long index) {
        return MEMORY_ACCESSOR.getInt(target, INT_ARRAY_BASE_OFFSET + (index * INT_ARRAY_INDEX_SCALE));
    }

    static void putInt(int[] target, long index, int value) {
        MEMORY_ACCESSOR.putInt(target, INT_ARRAY_BASE_OFFSET + (index * INT_ARRAY_INDEX_SCALE), value);
    }

    static long getLong(long[] target, long index) {
        return MEMORY_ACCESSOR.getLong(
                target, LONG_ARRAY_BASE_OFFSET + (index * LONG_ARRAY_INDEX_SCALE));
    }

    static void putLong(long[] target, long index, long value) {
        MEMORY_ACCESSOR.putLong(
                target, LONG_ARRAY_BASE_OFFSET + (index * LONG_ARRAY_INDEX_SCALE), value);
    }

    static boolean getBoolean(boolean[] target, long index) {
        return MEMORY_ACCESSOR.getBoolean(
                target, BOOLEAN_ARRAY_BASE_OFFSET + (index * BOOLEAN_ARRAY_INDEX_SCALE));
    }

    static void putBoolean(boolean[] target, long index, boolean value) {
        MEMORY_ACCESSOR.putBoolean(
                target, BOOLEAN_ARRAY_BASE_OFFSET + (index * BOOLEAN_ARRAY_INDEX_SCALE), value);
    }

    static float getFloat(float[] target, long index) {
        return MEMORY_ACCESSOR.getFloat(
                target, FLOAT_ARRAY_BASE_OFFSET + (index * FLOAT_ARRAY_INDEX_SCALE));
    }

    static void putFloat(float[] target, long index, float value) {
        MEMORY_ACCESSOR.putFloat(
                target, FLOAT_ARRAY_BASE_OFFSET + (index * FLOAT_ARRAY_INDEX_SCALE), value);
    }

    static double getDouble(double[] target, long index) {
        return MEMORY_ACCESSOR.getDouble(
                target, DOUBLE_ARRAY_BASE_OFFSET + (index * DOUBLE_ARRAY_INDEX_SCALE));
    }

    static void putDouble(double[] target, long index, double value) {
        MEMORY_ACCESSOR.putDouble(
                target, DOUBLE_ARRAY_BASE_OFFSET + (index * DOUBLE_ARRAY_INDEX_SCALE), value);
    }

    static Object getObject(Object[] target, long index) {
        return MEMORY_ACCESSOR.getObject(
                target, OBJECT_ARRAY_BASE_OFFSET + (index * OBJECT_ARRAY_INDEX_SCALE));
    }

    static void putObject(Object[] target, long index, Object value) {
        MEMORY_ACCESSOR.putObject(
                target, OBJECT_ARRAY_BASE_OFFSET + (index * OBJECT_ARRAY_INDEX_SCALE), value);
    }

    static void copyMemory(byte[] src, long srcIndex, long targetOffset, long length) {
        MEMORY_ACCESSOR.copyMemory(src, srcIndex, targetOffset, length);
    }

    static void copyMemory(long srcOffset, byte[] target, long targetIndex, long length) {
        MEMORY_ACCESSOR.copyMemory(srcOffset, target, targetIndex, length);
    }

    static void copyMemory(byte[] src, long srcIndex, byte[] target, long targetIndex, long length) {
        System.arraycopy(src, (int) srcIndex, target, (int) targetIndex, (int) length);
    }

    static byte getByte(long address) {
        return MEMORY_ACCESSOR.getByte(address);
    }

    static void putByte(long address, byte value) {
        MEMORY_ACCESSOR.putByte(address, value);
    }

    static int getInt(long address) {
        return MEMORY_ACCESSOR.getInt(address);
    }

    static void putInt(long address, int value) {
        MEMORY_ACCESSOR.putInt(address, value);
    }

    static long getLong(long address) {
        return MEMORY_ACCESSOR.getLong(address);
    }

    static void putLong(long address, long value) {
        MEMORY_ACCESSOR.putLong(address, value);
    }

    /**
     * Gets the offset of the {@code address} field of the given direct {@link ByteBuffer}.
     */
    static long addressOffset(ByteBuffer buffer) {
        return MEMORY_ACCESSOR.getLong(buffer, BUFFER_ADDRESS_OFFSET);
    }

    static Object getStaticObject(Field field) {
        return MEMORY_ACCESSOR.getStaticObject(field);
    }

    /**
     * Gets the {@code sun.misc.Unsafe} instance, or {@code null} if not available on this platform.
     */
    static sun.misc.Unsafe getUnsafe() {
        sun.misc.Unsafe unsafe = null;
        try {
            unsafe =
                    AccessController.doPrivileged(
                            new PrivilegedExceptionAction<sun.misc.Unsafe>() {
                                @Override
                                public sun.misc.Unsafe run() throws Exception {
                                    Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;

                                    for (Field f : k.getDeclaredFields()) {
                                        f.setAccessible(true);
                                        Object x = f.get(null);
                                        if (k.isInstance(x)) {
                                            return k.cast(x);
                                        }
                                    }
                                    // The sun.misc.Unsafe field does not exist.
                                    return null;
                                }
                            });
        } catch (Throwable e) {
            // Catching Throwable here due to the fact that Google AppEngine raises NoClassDefFoundError
            // for Unsafe.
        }
        return unsafe;
    }

    /**
     * Get a {@link MemoryAccessor} appropriate for the platform, or null if not supported.
     */
    private static MemoryAccessor getMemoryAccessor() {
        if (UNSAFE == null) {
            return null;
        }
        if (Android.isOnAndroidDevice()) {
            if (IS_ANDROID_64) {
                return new Android64MemoryAccessor(UNSAFE);
            } else if (IS_ANDROID_32) {
                return new Android32MemoryAccessor(UNSAFE);
            } else {
                return null;
            }
        }

        return new JvmMemoryAccessor(UNSAFE);
    }

    private static boolean supportsUnsafeArrayOperations() {
        if (MEMORY_ACCESSOR == null) {
            return false;
        }
        return MEMORY_ACCESSOR.supportsUnsafeArrayOperations();
    }

    private static boolean supportsUnsafeByteBufferOperations() {
        if (MEMORY_ACCESSOR == null) {
            return false;
        }
        return MEMORY_ACCESSOR.supportsUnsafeByteBufferOperations();
    }

    static boolean determineAndroidSupportByAddressSize(Class<?> addressClass) {
        if (!Android.isOnAndroidDevice()) {
            return false;
        }
        try {
            Class<?> clazz = MEMORY_CLASS;
            clazz.getMethod("peekLong", addressClass, boolean.class);
            clazz.getMethod("pokeLong", addressClass, long.class, boolean.class);
            clazz.getMethod("pokeInt", addressClass, int.class, boolean.class);
            clazz.getMethod("peekInt", addressClass, boolean.class);
            clazz.getMethod("pokeByte", addressClass, byte.class);
            clazz.getMethod("peekByte", addressClass);
            clazz.getMethod("pokeByteArray", addressClass, byte[].class, int.class, int.class);
            clazz.getMethod("peekByteArray", addressClass, byte[].class, int.class, int.class);
            return true;
        } catch (Throwable t) {
            return false;
        }
    }

    /**
     * Finds the address field within a direct {@link Buffer}.
     */
    private static Field bufferAddressField() {
        if (Android.isOnAndroidDevice()) {
            // Old versions of Android had renamed the address field to 'effectiveDirectAddress', but
            // recent versions of Android (>M?) use the OpenJDK implementation. Fall through in that case.
            Field field = field(Buffer.class, "effectiveDirectAddress");
            if (field != null) {
                return field;
            }
        }
        Field field = field(Buffer.class, "address");
        return field != null && field.getType() == long.class ? field : null;
    }

    /**
     * Returns the index of the first byte where left and right differ, in the range [0, 8]. If {@code
     * left == right}, the result will be 8, otherwise less than 8.
     *
     * <p>This counts from the *first* byte, which may be the most or least significant byte depending
     * on the system endianness.
     */
    private static int firstDifferingByteIndexNativeEndian(long left, long right) {
        int n =
                IS_BIG_ENDIAN
                        ? Long.numberOfLeadingZeros(left ^ right)
                        : Long.numberOfTrailingZeros(left ^ right);
        return n >> 3;
    }

    /**
     * Returns the lowest {@code index} such that {@code 0 <= index < length} and {@code left[leftOff
     * + index] != right[rightOff + index]}. If no such value exists -- if {@code left} and {@code
     * right} match up to {@code length} bytes from their respective offsets -- returns -1.
     *
     * <p>{@code leftOff + length} must be less than or equal to {@code left.length}, and the same for
     * {@code right}.
     */
    static int mismatch(byte[] left, int leftOff, byte[] right, int rightOff, int length) {
        if (leftOff < 0
                || rightOff < 0
                || length < 0
                || leftOff + length > left.length
                || rightOff + length > right.length) {
            throw new IndexOutOfBoundsException();
        }

        int index = 0;
        if (HAS_UNSAFE_ARRAY_OPERATIONS) {
            int leftAlignment = (BYTE_ARRAY_ALIGNMENT + leftOff) & STRIDE_ALIGNMENT_MASK;

            // Most CPUs handle getting chunks of bytes better on addresses that are a multiple of 4
            // or 8.
            // We walk one byte at a time until the left address, at least, is a multiple of 8.
            // If the right address is, too, so much the better.
            for (;
                 index < length && (leftAlignment & STRIDE_ALIGNMENT_MASK) != 0;
                 index++, leftAlignment++) {
                if (left[leftOff + index] != right[rightOff + index]) {
                    return index;
                }
            }

            // Stride!  Grab eight bytes at a time from left and right and check them for equality.

            int strideLength = ((length - index) & ~STRIDE_ALIGNMENT_MASK) + index;
            // strideLength is the point where we want to stop striding: it differs from index by
            // a multiple of STRIDE, and it's the largest such number <= length.

            for (; index < strideLength; index += STRIDE) {
                long leftLongWord = getLong(left, BYTE_ARRAY_BASE_OFFSET + leftOff + index);
                long rightLongWord = getLong(right, BYTE_ARRAY_BASE_OFFSET + rightOff + index);
                if (leftLongWord != rightLongWord) {
                    // one of these eight bytes differ!  use a helper to find out which one
                    return index + firstDifferingByteIndexNativeEndian(leftLongWord, rightLongWord);
                }
            }
        }

        // If we were able to stride, there are at most STRIDE - 1 bytes left to compare.
        // If we weren't, then this loop covers the whole thing.
        for (; index < length; index++) {
            if (left[leftOff + index] != right[rightOff + index]) {
                return index;
            }
        }
        return -1;
    }

    /**
     * Returns the offset of the provided field, or {@code -1} if {@code sun.misc.Unsafe} is not
     * available.
     */
    private static long fieldOffset(Field field) {
        return field == null || MEMORY_ACCESSOR == null ? -1 : MEMORY_ACCESSOR.objectFieldOffset(field);
    }

    /**
     * Gets the field with the given name within the class, or {@code null} if not found.
     */
    private static Field field(Class<?> clazz, String fieldName) {
        Field field;
        try {
            field = clazz.getDeclaredField(fieldName);
        } catch (Throwable t) {
            // Failed to access the fields.
            field = null;
        }
        return field;
    }

    private abstract static class MemoryAccessor {

        sun.misc.Unsafe unsafe;

        MemoryAccessor(sun.misc.Unsafe unsafe) {
            this.unsafe = unsafe;
        }

        public final long objectFieldOffset(Field field) {
            return unsafe.objectFieldOffset(field);
        }

        public final int arrayBaseOffset(Class<?> clazz) {
            return unsafe.arrayBaseOffset(clazz);
        }

        public final int arrayIndexScale(Class<?> clazz) {
            return unsafe.arrayIndexScale(clazz);
        }

        public abstract Object getStaticObject(Field field);

        // Relative Address Operations ---------------------------------------------

        // Indicates whether the following relative address operations are supported
        // by this memory accessor.
        public boolean supportsUnsafeArrayOperations() {
            if (unsafe == null) {
                return false;
            }
            try {
                Class<?> clazz = unsafe.getClass();
                clazz.getMethod("objectFieldOffset", Field.class);
                clazz.getMethod("arrayBaseOffset", Class.class);
                clazz.getMethod("arrayIndexScale", Class.class);
                clazz.getMethod("getInt", Object.class, long.class);
                clazz.getMethod("putInt", Object.class, long.class, int.class);
                clazz.getMethod("getLong", Object.class, long.class);
                clazz.getMethod("putLong", Object.class, long.class, long.class);
                clazz.getMethod("getObject", Object.class, long.class);
                clazz.getMethod("putObject", Object.class, long.class, Object.class);

                return true;
            } catch (Throwable e) {
                logMissingMethod(e);
            }
            return false;
        }

        public abstract byte getByte(Object target, long offset);

        public abstract void putByte(Object target, long offset, byte value);

        public final int getInt(Object target, long offset) {
            return unsafe.getInt(target, offset);
        }

        public final void putInt(Object target, long offset, int value) {
            unsafe.putInt(target, offset, value);
        }

        public final long getLong(Object target, long offset) {
            return unsafe.getLong(target, offset);
        }

        public final void putLong(Object target, long offset, long value) {
            unsafe.putLong(target, offset, value);
        }

        public abstract boolean getBoolean(Object target, long offset);

        public abstract void putBoolean(Object target, long offset, boolean value);

        public abstract float getFloat(Object target, long offset);

        public abstract void putFloat(Object target, long offset, float value);

        public abstract double getDouble(Object target, long offset);

        public abstract void putDouble(Object target, long offset, double value);

        public final Object getObject(Object target, long offset) {
            return unsafe.getObject(target, offset);
        }

        public final void putObject(Object target, long offset, Object value) {
            unsafe.putObject(target, offset, value);
        }

        // Absolute Address Operations --------------------------------------------

        // Indicates whether the following absolute address operations are
        // supported by this memory accessor.
        public boolean supportsUnsafeByteBufferOperations() {
            if (unsafe == null) {
                return false;
            }
            try {
                Class<?> clazz = unsafe.getClass();
                // Methods for getting direct buffer address.
                clazz.getMethod("objectFieldOffset", Field.class);
                clazz.getMethod("getLong", Object.class, long.class);

                if (bufferAddressField() == null) {
                    return false;
                }

                return true;
            } catch (Throwable e) {
                logMissingMethod(e);
            }
            return false;
        }

        public abstract byte getByte(long address);

        public abstract void putByte(long address, byte value);

        public abstract int getInt(long address);

        public abstract void putInt(long address, int value);

        public abstract long getLong(long address);

        public abstract void putLong(long address, long value);

        public abstract void copyMemory(long srcOffset, byte[] target, long targetIndex, long length);

        public abstract void copyMemory(byte[] src, long srcIndex, long targetOffset, long length);
    }

    private static final class JvmMemoryAccessor extends MemoryAccessor {

        JvmMemoryAccessor(sun.misc.Unsafe unsafe) {
            super(unsafe);
        }

        @Override
        public Object getStaticObject(Field field) {
            return getObject(unsafe.staticFieldBase(field), unsafe.staticFieldOffset(field));
        }

        @Override
        public boolean supportsUnsafeArrayOperations() {
            if (!super.supportsUnsafeArrayOperations()) {
                return false;
            }

            try {
                Class<?> clazz = unsafe.getClass();
                clazz.getMethod("getByte", Object.class, long.class);
                clazz.getMethod("putByte", Object.class, long.class, byte.class);
                clazz.getMethod("getBoolean", Object.class, long.class);
                clazz.getMethod("putBoolean", Object.class, long.class, boolean.class);
                clazz.getMethod("getFloat", Object.class, long.class);
                clazz.getMethod("putFloat", Object.class, long.class, float.class);
                clazz.getMethod("getDouble", Object.class, long.class);
                clazz.getMethod("putDouble", Object.class, long.class, double.class);

                return true;
            } catch (Throwable e) {
                logMissingMethod(e);
            }
            return false;
        }

        @Override
        public byte getByte(Object target, long offset) {
            return unsafe.getByte(target, offset);
        }

        @Override
        public void putByte(Object target, long offset, byte value) {
            unsafe.putByte(target, offset, value);
        }

        @Override
        public boolean getBoolean(Object target, long offset) {
            return unsafe.getBoolean(target, offset);
        }

        @Override
        public void putBoolean(Object target, long offset, boolean value) {
            unsafe.putBoolean(target, offset, value);
        }

        @Override
        public float getFloat(Object target, long offset) {
            return unsafe.getFloat(target, offset);
        }

        @Override
        public void putFloat(Object target, long offset, float value) {
            unsafe.putFloat(target, offset, value);
        }

        @Override
        public double getDouble(Object target, long offset) {
            return unsafe.getDouble(target, offset);
        }

        @Override
        public void putDouble(Object target, long offset, double value) {
            unsafe.putDouble(target, offset, value);
        }

        @Override
        public boolean supportsUnsafeByteBufferOperations() {
            if (!super.supportsUnsafeByteBufferOperations()) {
                return false;
            }

            try {
                Class<?> clazz = unsafe.getClass();
                clazz.getMethod("getByte", long.class);
                clazz.getMethod("putByte", long.class, byte.class);
                clazz.getMethod("getInt", long.class);
                clazz.getMethod("putInt", long.class, int.class);
                clazz.getMethod("getLong", long.class);
                clazz.getMethod("putLong", long.class, long.class);
                clazz.getMethod("copyMemory", long.class, long.class, long.class);
                clazz.getMethod(
                        "copyMemory", Object.class, long.class, Object.class, long.class, long.class);
                return true;
            } catch (Throwable e) {
                logMissingMethod(e);
            }
            return false;
        }

        @Override
        public byte getByte(long address) {
            return unsafe.getByte(address);
        }

        @Override
        public void putByte(long address, byte value) {
            unsafe.putByte(address, value);
        }

        @Override
        public int getInt(long address) {
            return unsafe.getInt(address);
        }

        @Override
        public void putInt(long address, int value) {
            unsafe.putInt(address, value);
        }

        @Override
        public long getLong(long address) {
            return unsafe.getLong(address);
        }

        @Override
        public void putLong(long address, long value) {
            unsafe.putLong(address, value);
        }

        @Override
        public void copyMemory(long srcOffset, byte[] target, long targetIndex, long length) {
            unsafe.copyMemory(null, srcOffset, target, BYTE_ARRAY_BASE_OFFSET + targetIndex, length);
        }

        @Override
        public void copyMemory(byte[] src, long srcIndex, long targetOffset, long length) {
            unsafe.copyMemory(src, BYTE_ARRAY_BASE_OFFSET + srcIndex, null, targetOffset, length);
        }
    }

    private static final class Android64MemoryAccessor extends MemoryAccessor {

        Android64MemoryAccessor(sun.misc.Unsafe unsafe) {
            super(unsafe);
        }

        @Override
        public Object getStaticObject(Field field) {
            try {
                return field.get(null);
            } catch (IllegalAccessException e) {
                return null;
            }
        }

        @Override
        public byte getByte(Object target, long offset) {
            if (IS_BIG_ENDIAN) {
                return getByteBigEndian(target, offset);
            } else {
                return getByteLittleEndian(target, offset);
            }
        }

        @Override
        public void putByte(Object target, long offset, byte value) {
            if (IS_BIG_ENDIAN) {
                putByteBigEndian(target, offset, value);
            } else {
                putByteLittleEndian(target, offset, value);
            }
        }

        @Override
        public boolean getBoolean(Object target, long offset) {
            if (IS_BIG_ENDIAN) {
                return getBooleanBigEndian(target, offset);
            } else {
                return getBooleanLittleEndian(target, offset);
            }
        }

        @Override
        public void putBoolean(Object target, long offset, boolean value) {
            if (IS_BIG_ENDIAN) {
                putBooleanBigEndian(target, offset, value);
            } else {
                putBooleanLittleEndian(target, offset, value);
            }
        }

        @Override
        public float getFloat(Object target, long offset) {
            return Float.intBitsToFloat(getInt(target, offset));
        }

        @Override
        public void putFloat(Object target, long offset, float value) {
            putInt(target, offset, Float.floatToIntBits(value));
        }

        @Override
        public double getDouble(Object target, long offset) {
            return Double.longBitsToDouble(getLong(target, offset));
        }

        @Override
        public void putDouble(Object target, long offset, double value) {
            putLong(target, offset, Double.doubleToLongBits(value));
        }

        @Override
        public boolean supportsUnsafeByteBufferOperations() {
            return false;
        }

        @Override
        public byte getByte(long address) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void putByte(long address, byte value) {
            throw new UnsupportedOperationException();
        }

        @Override
        public int getInt(long address) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void putInt(long address, int value) {
            throw new UnsupportedOperationException();
        }

        @Override
        public long getLong(long address) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void putLong(long address, long value) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void copyMemory(long srcOffset, byte[] target, long targetIndex, long length) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void copyMemory(byte[] src, long srcIndex, long targetOffset, long length) {
            throw new UnsupportedOperationException();
        }
    }

    private static final class Android32MemoryAccessor extends MemoryAccessor {

        /**
         * Mask used to convert a 64 bit memory address to a 32 bit address.
         */
        private static final long SMALL_ADDRESS_MASK = 0x00000000FFFFFFFF;

        /**
         * Truncate a {@code long} address into a short {@code int} address.
         */
        private static int smallAddress(long address) {
            return (int) (SMALL_ADDRESS_MASK & address);
        }

        Android32MemoryAccessor(sun.misc.Unsafe unsafe) {
            super(unsafe);
        }

        @Override
        public Object getStaticObject(Field field) {
            try {
                return field.get(null);
            } catch (IllegalAccessException e) {
                return null;
            }
        }

        @Override
        public byte getByte(Object target, long offset) {
            if (IS_BIG_ENDIAN) {
                return getByteBigEndian(target, offset);
            } else {
                return getByteLittleEndian(target, offset);
            }
        }

        @Override
        public void putByte(Object target, long offset, byte value) {
            if (IS_BIG_ENDIAN) {
                putByteBigEndian(target, offset, value);
            } else {
                putByteLittleEndian(target, offset, value);
            }
        }

        @Override
        public boolean getBoolean(Object target, long offset) {
            if (IS_BIG_ENDIAN) {
                return getBooleanBigEndian(target, offset);
            } else {
                return getBooleanLittleEndian(target, offset);
            }
        }

        @Override
        public void putBoolean(Object target, long offset, boolean value) {
            if (IS_BIG_ENDIAN) {
                putBooleanBigEndian(target, offset, value);
            } else {
                putBooleanLittleEndian(target, offset, value);
            }
        }

        @Override
        public float getFloat(Object target, long offset) {
            return Float.intBitsToFloat(getInt(target, offset));
        }

        @Override
        public void putFloat(Object target, long offset, float value) {
            putInt(target, offset, Float.floatToIntBits(value));
        }

        @Override
        public double getDouble(Object target, long offset) {
            return Double.longBitsToDouble(getLong(target, offset));
        }

        @Override
        public void putDouble(Object target, long offset, double value) {
            putLong(target, offset, Double.doubleToLongBits(value));
        }

        @Override
        public boolean supportsUnsafeByteBufferOperations() {
            return false;
        }

        @Override
        public byte getByte(long address) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void putByte(long address, byte value) {
            throw new UnsupportedOperationException();
        }

        @Override
        public int getInt(long address) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void putInt(long address, int value) {
            throw new UnsupportedOperationException();
        }

        @Override
        public long getLong(long address) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void putLong(long address, long value) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void copyMemory(long srcOffset, byte[] target, long targetIndex, long length) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void copyMemory(byte[] src, long srcIndex, long targetOffset, long length) {
            throw new UnsupportedOperationException();
        }
    }

    private static byte getByteBigEndian(Object target, long offset) {
        return (byte) ((getInt(target, offset & ~3) >>> ((~offset & 3) << 3)) & 0xFF);
    }

    private static byte getByteLittleEndian(Object target, long offset) {
        return (byte) ((getInt(target, offset & ~3) >>> ((offset & 3) << 3)) & 0xFF);
    }

    private static void putByteBigEndian(Object target, long offset, byte value) {
        int intValue = getInt(target, offset & ~3);
        int shift = ((~(int) offset) & 3) << 3;
        int output = (intValue & ~(0xFF << shift)) | ((0xFF & value) << shift);
        putInt(target, offset & ~3, output);
    }

    private static void putByteLittleEndian(Object target, long offset, byte value) {
        int intValue = getInt(target, offset & ~3);
        int shift = (((int) offset) & 3) << 3;
        int output = (intValue & ~(0xFF << shift)) | ((0xFF & value) << shift);
        putInt(target, offset & ~3, output);
    }

    private static boolean getBooleanBigEndian(Object target, long offset) {
        return getByteBigEndian(target, offset) != 0;
    }

    private static boolean getBooleanLittleEndian(Object target, long offset) {
        return getByteLittleEndian(target, offset) != 0;
    }

    private static void putBooleanBigEndian(Object target, long offset, boolean value) {
        putByteBigEndian(target, offset, (byte) (value ? 1 : 0));
    }

    private static void putBooleanLittleEndian(Object target, long offset, boolean value) {
        putByteLittleEndian(target, offset, (byte) (value ? 1 : 0));
    }

    private static void logMissingMethod(Throwable e) {
        Logger.getLogger(UnsafeUtil.class.getName())
                .log(
                        Level.WARNING,
                        "platform method missing - proto runtime falling back to safer methods: " + e);
    }
}
